1. Field of the Invention
The present invention relates to an ink, an ink cartridge and an ink jet recording method.
2. Description of the Related Art
An ink jet recording method is such a recording method that minute droplets of an ink are applied to a recording medium such as plain paper to form an image, and is rapidly spread owing to low price of an apparatus itself and improvement of recording speed. In general, a recorded article obtained by the ink jet recording method is low in fastness properties of an image thereof compared with a silver salt photograph. In particular, when the recorded article is exposed to light, humidity, heat or environmental gas present in air, such as an ozone gas for a long period of time, there is a problem that a coloring material of the recorded article is deteriorated to easily cause change in color tone or fading of the image.
In the ink jet recording method, inks each having, for example, a yellow, magenta, cyan, or black hue are used. It has heretofore been acknowledged that the ink having a black hue out of those inks needs to be improved in terms of its performance such as ozone resistance, and various proposals have been made on the improvement. For example, there has been a proposal on an ink containing an azo dye, in which the number of conjugated n-electrons of an aromatic ring that is not directly bonded to an azo group is specified, for improving the ozone resistance of an image to be recorded (see Japanese Patent Application Laid-Open No. 2005-139427). In addition, there has been a proposal on an ink using a polyazo compound (see Japanese Patent Application Laid-Open Nos. 2008-169374, 2012-046559, and 2002-332426). Japanese Patent Application Laid-Open No. 2002-332426 describes that with such ink, the humidity resistance of an image to be recorded improves.
Meanwhile, there has been a proposal on an ink containing a coloring material having a carboxy group and an alkali metal ion for improving ink jet characteristics such as recoverability from fixation (see Japanese Patent Application Laid-Open No. 2003-206421).